Abstract
[Purpose] The purpose of this study was to determine the effect of the cocontraction of masticatory muscles during neck stabilization exercises on changes in the thickness of the neck flexors. [Subjects and Methods] Twenty subjects performed neck stabilization only exercise and neck stabilization exercise with simultaneous contraction of the masticatory muscles. Changes in the thickness of the longus colli and sternocleidomastoid were then measured by ultrasound. [Results] The thickness of the longus colli increased significantly fallowing cocontraction of the masticatory muscles and neck stabilization exercise, whereas the exercise method used had no significant effect on the thickness of the sternocleidomastoid. [Conclusion] Cocontraction of the masticatory muscles during neck stabilization exercise is helpful in increasing the thickness of longus colli muscle.